The present invention relates to the sublimation and pyrolysis of hydrocarbons. In particular, the present invention relates to the sublimation and pyrolysis of hydrocarbons using radio frequency (RF) energy amplified by a ring resonator.
As the world's standard crude oil reserves are depleted, and the continued demand for oil causes oil prices to rise, attempts have been made to process all manner of hydrocarbons in increasingly varied ways. For example, attempts have been made to heat subsurface heavy oil bearing formations using steam, microwave energy and RF energy. However, these attempts have been generally inefficient and costly.
Sublimation or pyrolysis of substances such as coal and shale oil may yield valuable products, such as natural gas. Sublimation is essentially taking a material from its solid phase to its gaseous phase without the presence of a liquid phase. Pyrolysis, on the other hand, involves the chemical decomposition of organic substances by heating to break down hydrogen bonds. Such a process may produce natural gas from the sublimated or pyrolyzed substances with low greenhouse gas emissions. However, existing technologies require more energy to sublimate or pyrolyze substances such as coal or shale oil than the energy that is produced.
Pyrolysis differs from other processes (combustion and hydrolysis) in which the reactions do not involve oxygen or water. Pyrolysis of organic substances typically produces gas and liquid products and leave behind a carbon rich solid residue. In many industrial applications, the process is done under pressure and at operating temperatures above 430° C. Since pyrolysis is endothermic, problems with current technologies exist in which biomass substances are not receiving enough heat to efficiently pyrolyze and result in poor quality. For such cases, it becomes imperative for an initiation reaction to be used to enhance the amount of heat applied to the hydrocarbon material.
As the organic chemical structures of various hydrocarbons ages, the aromaticity (defined as the ratio of aromatic carbon to total carbon) increases. These aromatic structures are chains of carbons that are targeted for breaking during heating processes. In order for the production of natural gas to occur, these large complex structures break during reactions and thus, increase the solubility of the organic portion of the substance. Some of these reactions are (but not limited to) cracking, alkylation, hydrogenation, and depolymerization.
Thus, various hydrocarbon materials must be extensively processed in order to achieve maximum fuel production. In industry, upgrading facilities are used in order to further make the material usable and more valuable. It is possible that the RF energy applied in this technology could be used to also change the molecular structure of the material by breaking it into smaller components bypassing the need for the hydrocarbons to be processed and treated at upgrading facilities.
It is known that a resonant ring may be used to generate a very large electromagnetic field and to couple this RF power through a coupling mechanism to a reaction chamber. In order to achieve the high field amplitude required, the resonant mechanism referred hereafter as the ring most be in a state of resonance at its operating frequency. To effect this, the length of the ring has to be an integral number of guide wavelengths of the coupled wave. The waves coupled through the resonant ring, along with the directional coupler, create an effective power gain. The amplitude of this wave front can be tracked and measured throughout this process by appropriately incrementing the resonant ring. To build a resonant ring, two couplers of similar design are implemented with a coupling structure between them. The coupling structure can be of either waveguide or coaxial transmission line. The cavity provides the needed bandwidth to track the dependence of the cavity frequency to the dimension of the ring.